Boat Fuel Range Calculator
Calculate your cruising range and engine endurance from tank capacity, fuel consumption, and speed.
Includes safety reserve calculation.
Fuel planning for sea passages
Running out of fuel at sea is a serious emergency. Reliable fuel planning requires knowing three things: how much fuel you have available, how fast the engine burns it, and how fast the boat moves through the water.
Endurance (hours) = Usable fuel ÷ Fuel consumption rate Range (nm) = Endurance × Speed
Fuel consumption and speed
Diesel marine engines are most efficient at 60–80% of maximum throttle. Pushing above this increases fuel consumption dramatically while adding little speed. Most displacement motor-sailors and cruising yachts burn 2–6 litres per hour at cruising throttle, delivering 5–8 knots.
At hull speed, fuel consumption typically jumps significantly (40–100% more per hour) for only a marginal increase in speed. Backing off throttle by even 10% often reduces fuel burn by 20–30% while losing only 0.3–0.5 knots.
Safety reserve
Always keep a meaningful reserve. The standard recommendation is:
- 30% reserve for coastal passages (known distance, alternatives available)
- 40–50% reserve for offshore passages (weather delays, unexpected distance)
- Never plan to arrive with less than 1–2 hours of fuel remaining
This calculator applies your chosen reserve percentage before calculating usable range.
Using this calculator
Enter your actual tank capacity, not the manufacturer’s rated capacity — tanks are rarely 100% accessible. Enter your verified consumption figure from engine logs if available, or use the manufacturer’s rated consumption as an approximation.